Control method for an electric heating element with adapted power consumption, climate-control unit for carrying out the control method and motor vehicle having such a climate-control unit

Abstract

A description is given of a control method (500) for an electric heating element (108), which can be provided or is provided in an air-conducting duct (106) of a climate-control unit (100) of a motor vehicle (200), the method (500) comprising the following steps: determining (S501) a setpoint power consumption (P_soll_s) for a stationary operating point of the electric heating element (108); determining (S502) a setpoint temperature (T__soll_h) of the electric heating element (108) on the basis of the setpoint electrical power consumption (P_soll_s); determining (S503) a quantity of heat (dQ) to be supplied to the electric heating element (108) on the basis of the setpoint temperature (T_soll_h) and the actual temperature (T_ist_h) of the electric heating element (108); and determining (S504) an actual electrical power consumption (P_ist_h) of the electric heating element (108), wherein the actual electrical power consumption (P_ist_h) is calculated on the basis of the setpoint power consumption (P_soll_s) for the stationary operating point and a dynamic setpoint power consumption (P_soll_d). A climate-control unit and a motor vehicle are also described.

Description

[0001] AUDI AG 1 P23777

[0002] Control procedure for an electric heating element with adapted power consumption, air conditioning unit for carrying out the control procedure and motor vehicle with such an air conditioning unit

[0003] DESCRIPTION:

[0004] The invention relates to a control method for an electric heating element that can be provided or is provided in an air duct of an air conditioning unit of a motor vehicle. The invention further relates to an air conditioning unit with a control unit for executing the control method and a motor vehicle with such an air conditioning unit.

[0005] For example, EP 1 669 226 A1 discloses a model-based control method for an air conditioning system of a motor vehicle. Furthermore, DE10 2020 115 896 A1 discloses a method for controlling thermal management for the interior of a motor vehicle.

[0006] An electric (air) heating element is used to ensure that a desired air outlet temperature is provided by an air conditioning unit. A power balance is typically used to determine the required operating point of the air heater, so that setting steady-state operating points works well.

[0007] However, if the boundary conditions are changed, dynamic temperature deviations result, which can be summarized as follows:

[0008] If the air mass flow rate passing over the electric heating element is increased, this is followed by a temporary drop (dip) in the air temperature downstream of the electric heating element. If the air mass flow rate is reduced, this is followed by a temporary increase (overshoot) in the air temperature. Such an overshoot in air temperature (AUDI AG 2 P23777) can, in particular, lead to the shutdown of the air conditioning unit.

[0009] If a different target temperature is selected for the vehicle's interior in the climate control unit, the corresponding thermal effect on the airflow at the electric heating element can only occur with a significant delay. Furthermore, a change in the air inlet temperature also leads to similar increases (overshoot) or decreases (dip) in the air outlet temperature.

[0010] The object of the invention is to provide a control method for an electric heating element that avoids or at least reduces the aforementioned disadvantages. In particular, it aims to minimize, as far as possible, prolonged temperature changes in the air outlet temperature that are noticeable to vehicle occupants.

[0011] This problem is solved by a control method, an air conditioning unit, and a motor vehicle with the features of the respective independent patent claim. Advantageous embodiments with appropriate further developments are specified in the dependent patent claims.

[0012] A control method is therefore proposed for an electric heating element that can be provided or is provided in an air duct of an air conditioning unit of a motor vehicle, the method comprising the following steps:

[0013] Determining a target power consumption for a steady-state operating point of the electric heating element;

[0014] Determining a target temperature of the electric heating element based on the target electrical power consumption;

[0015] Determining the amount of heat to be supplied to the electric heating element based on the target temperature and the actual temperature of the electric heating element; and

[0016] Determining the actual electrical power consumption of the electrical heating element, where the actual electrical power consumption is based on AUDI AG 3 P23777

[0017] The target power consumption for the stationary operating point and a dynamic target power consumption is calculated.

[0018] The dynamic target power input serves to adjust the target power input known for a steady-state operating point in the manner of a feedforward control, in particular model-based, so that the electrical heating element is operated at least temporarily with an actual electrical power input that leads to a faster achievement of the desired air outlet temperature.

[0019] In this control method, the dynamic target power input can be calculated based on the amount of heat to be supplied, taking into account a gain factor.

[0020] The amplification factor can be determined depending on the minimum and / or maximum electrical power consumption of the electrical heating element.

[0021] In other words, the described control method allows the electric heating element to be operated at minimum, in particular zero, or maximum power for a specific (short) period of time, depending on the required amount of heat.

[0022] Also proposed is an air conditioning unit for a motor vehicle with at least partial electric drive, comprising at least one electric heating element arranged in an air duct downstream of a heat exchanger, in particular an evaporator, of a refrigeration system of the air conditioning unit, and a control unit designed to control the at least one electric heating element according to the method described above.

[0023] Furthermore, a motor vehicle with at least a partially electric drive and with such an air conditioning unit is proposed. AUDI AG 4 P23777

[0024] Further advantages and details of the invention will become apparent from the following description of embodiments with reference to the figures. These show:

[0025] Fig. 1 shows a simplified and schematic representation of a motor vehicle with an air conditioning unit;

[0026] Fig. 2 simplifies the steps of a tax procedure;

[0027] Fig. 3 shows various curve progressions of quantities of interest in connection with the control procedure in sub-figures or diagrams A) to C).

[0028] Fig. 1 shows a highly simplified and schematic representation of a motor vehicle 200 with an air conditioning unit 100, which is also only schematically illustrated.

[0029] The air conditioning unit 100 comprises at least one heat exchanger 102, in particular an evaporator for cooling and / or dehumidifying supplied air L. Downstream of the evaporator 102, simplified air ducts 104 for cooled air and air ducts 106 for air to be heated are shown.

[0030] The air conditioning unit 100 has electrical heating elements 108 in the air ducts 106, which are designed to heat the supplied air L as required.

[0031] The air ducts 104 and 106 can be (partially) opened or (partially) closed by means of actuators 110, such as flaps or the like. This allows the volume of air flowing through each air duct 104 or 106 to be adjusted. AUDI AG 5 P23777

[0032] The air conditioning unit 100 also includes a fan unit (not shown) designed to adjust the total volume of air flowing through the air conditioning unit 100.

[0033] The air conditioning unit also includes a control unit 150, which is configured to control individual components of the air conditioning unit 100, such as a refrigeration system connected to the evaporator 102 and / or the electric heating elements 108. The control unit 150 can also be part of a higher-level vehicle control unit.

[0034] Figure 2 illustrates a simplified and schematic sequence of a control method 500 for an electric heating element 108 of the air conditioning unit 100. Such a control method 500 can be implemented in a control unit 150, in particular in the form of control software or the like.

[0035] According to procedure 500, in step S501 a target power input P_soll_s is determined for a steady-state operating point of the electrical heating element 108.

[0036] According to step S502, a target temperature T_soll_h of the electrical heating element 108 is determined based on the electrical target power consumption P_soll_s.

[0037] According to step S503, a quantity of heat dQ to be supplied to the electric heating element 108 is determined based on the target temperature T_target_h and the actual temperature T_actual_h of the electric heating element 108.

[0038] In the procedure, according to step S504, the actual electrical power consumption P_actual_h of the electrical heating element 108 is determined, whereby the actual electrical power consumption P_actual_h is calculated based on the target power consumption P_target_s for the steady-state operating point and a dynamic target power consumption P_target_d. AUDI AG 6 P23777

[0039] In step S504, the calculation of the dynamic target power input P_target_d can be carried out based on the amount of heat to be supplied dQ, taking into account a gain factor K.

[0040] The amplification factor K can be calculated in particular as a function of the minimum and / or maximum electrical power consumption P_min, P_max of the electrical heating element 108.

[0041] The following calculation bases, in particular, can be used in procedure 500.

[0042] (1 ) P-target-S = k ■ A ■ (T_target_h - (T_target + T_L_in) / 2)

[0043] (2) T_soll_h = (P-Soll-S / k ■ A) + (T_soll + T_L_in) / 2)

[0044] (3) dQ = m_h ■ c_P_H ■ (T_soll_h - T_ist_h)

[0045] (4) P_soll_d = dQ ■ K

[0046] (5) P_is_h = P_should_s + P_should_d

[0047] This includes:

[0048] A considered contact area of ​​the heating element c_P_H specific heat capacity of the electric heating element dQ amount of heat to be supplied to the electric heating element k heat transfer coefficient

[0049] K Amplification factor m_h Mass of the electrical heating element

[0050] P_ist_h Actual power consumption of the electric heating element

[0051] P_soll_d dynamic target power consumption

[0052] P_soll_s Target power consumption of the electrical heating element for a steady-state operating point AUDI AG 7 P23777

[0053] T_ist_h Actual temperature of the electric heating element

[0054] T_L_in air temperature before (inlet side) electric heating element

[0055] T_soll_h Target temperature of the electric heating element

[0056] The method 500 presented here, with which a kind of pre-control of the electrical heating element 108 is achieved, will be explained below with reference to Fig. 3 and the diagrams A to C shown therein.

[0057] Fig. 3A shows the exemplary course of different (air) temperature curves over a period of approximately 900 seconds.

[0058] Fig. 3B shows the exemplary course of a target power consumption P_target_s for steady-state operating points and an actual power consumption P_actual_h over the same period of 900 seconds.

[0059] Fig. 3C shows the exemplary course of an air mass flow using a blower device of an air conditioning unit over the same period of 900 seconds.

[0060] According to the curve T_L_in (dashed line) in Fig. 3A, the temperature of the air entering the electrical heating element 108 is approximately 5°C, with a temporary increase to approximately 15°C during the period of approximately 620 to 780 seconds.

[0061] According to the curve T_soll (dotted line) in Fig. 3A, a Sol I outlet air temperature of 20°C is targeted, with a temporary increase to about 30°C occurring during the period of about 380 to 500 seconds.

[0062] According to the single curve shown in Fig. 3C, the air mass flow is initially set to approximately 70 kg / h. Over a period of approximately 120 to 250 seconds, the air mass flow is temporarily increased to approximately 170 kg / h. Subsequently, the air mass flow is maintained at a constant level of approximately 80 kg / h for a period of approximately 260 to 900 seconds. AUDI AG 8 P23777

[0063] Figure 3B shows that the conventional electrical target power input P_soll_s (dashed line) for steady-state operating points is set to different discrete values ​​in order to achieve the Sol I outlet air temperature T_soll (Figure 3A) as closely as possible.

[0064] With such a conventional target electrical power input P_target_s, the (actual) air outlet temperature T_L_out (dashed line) shown in Fig. 3A is obtained. With increasing air mass flow (Fig. 3C) from about 120 seconds onwards, a decrease or drop in the air outlet temperature T_L_out is evident. With a reduction in air mass flow (Fig. 3C) from about 270 seconds onwards, an increase or overshoot in the air outlet temperature T_L_out is evident.

[0065] When the target outlet temperature T_soll is increased (at 380 seconds), the air outlet temperature T_L_out follows the power consumption (P_soll_s) with a time delay of approximately 50 to 60 seconds when using conventional control. The same is observed when the target outlet temperature T_soll is decreased (at 500 seconds).

[0066] If the air inlet temperature T_L_in increases (Fig. 3A at approximately 620 seconds), a further increase or overshoot of the air outlet temperature T_L_out is evident.

[0067] Figure 3A also shows that the temperature T_h of the heating element rises and falls with a delay due to the discrete power input setting (Figure 3B). It is evident that the behavior of the air outlet temperature T_L_out, in particular its drop below and rise above the target outlet air temperature T_soll, is related to or dependent on the discrete power input settings.

[0068] According to the procedure presented here, the target power consumption P_target_s is corrected to the optimized value P_actual_h. For this purpose, the dynamic target power consumption P_target_d is determined and used based on the amount of heat to be supplied to the heating element and the correction factor.

[0069] This leads, for example, at time 120 seconds (increasing the air mass flow, Fig. 3C), to a briefly increased power consumption P_ist_h of approximately 1300 W instead of the approximately 800 W typical for steady-state operating points. At time 250 seconds, this leads, for example, to a briefly reduced power consumption, in particular to 0 W (zero watts).

[0070] At approximately 380 seconds, when the target outlet air temperature (T_soll) increases to 30°C, the power consumption (P_ist_h) is briefly increased, specifically set to the maximum possible power consumption of the heating element, approximately 2100 W. At approximately 500 seconds, when the target outlet temperature (T_soll) decreases to 20°C, the power consumption (P_ist_h) is reduced for several seconds, specifically to 0 W (zero watts).

[0071] When the temperature T_L_in of the air entering the electric heating element 108 is increased or decreased, the power consumption P_ist_h is briefly decreased or increased, respectively.

[0072] In other words, the various peaks or peaks upwards and downwards of the curve of the actual power consumption P_actual_h show that the target power consumption P_target_s is corrected by the above-described proportion of the dynamic target power consumption P_target_d, which depends on the amount of heat to be supplied dQ and the correction factor K.

[0073] As a result of the method with the optimized power consumption P_ist_h, an optimized air outlet temperature T_opt_L_out is achieved (Fig. 3A, solid line). It is evident that with the optimized air outlet temperature T_opt_L_out, no dips or overshoots occur as with the conventionally controlled air outlet temperature T_L_out. Furthermore, AUDI AG 10 P23777, the optimized air outlet temperature T_opt_L_out also follows the changing target outlet temperature T_soll with a significantly shorter time interval (approximately 380 to 500 seconds) compared to the conventionally controlled air outlet temperature T_L_out.

[0074] In other words: If one considers the optimized air outlet temperature T_opt_L_out, which results from the control method proposed here, in comparison to a conventional control T_L_out, a significantly better tracking behavior as well as a significantly better disturbance compensation is evident.

[0075] Figure 3A also shows that, due to the optimized power consumption P_ist_h, an optimized temperature T_opt_h of the heating element occurs, so that the heating element is heated or cooled down faster compared to the curve T_h.

Claims

AUDI AG 11 P23777 PATENT CLAIMS:

1. Control method (500) for an electric heating element (108) that can be provided or is provided in an air-conducting duct (106) of an air conditioning unit (100) of a motor vehicle (200), wherein the method (500) comprises the following steps: Determine (S501 ) a target power input (P_target_s) for a steady-state operating point of the electrical heating element (108); Determining (S502) a target temperature (T_target_h) of the electrical heating element (108) based on the electrical target power consumption (P_target_s); Determining (S503) a quantity of heat (dQ) to be supplied to the electric heating element (108) based on the target temperature (T_target_h) and the actual temperature (T_actual_h) of the electric heating element (108); characterized by Determine (S504) an actual electrical power consumption (P_actual_h) of the electrical heating element (108), wherein the actual electrical power consumption (P_actual_h) is calculated based on the target power consumption (P_target_s) for the steady-state operating point and a dynamic target power consumption (P_target_d).

2. Control method (500) according to claim 1 , characterized in that the dynamic target power input (P_target_d) is calculated based on the amount of heat to be supplied (dQ) taking into account a gain factor (K).

3. Control method (500) according to claim 2, wherein the amplification factor (K) is determined as a function of the minimum and / or maximum electrical power input (P_min, P_max) of the electrical heating element (108).

4. Air conditioning unit (100) for a motor vehicle (200) with at least partial electric drive, with at least one electric heating element AUDI AG 12 P23777 element (108) which is arranged in an air duct (106) downstream of a heat exchanger (102), in particular evaporator, of a refrigeration system of the air conditioning unit (100), and with a control unit (150) which is configured to control the at least one electrical heating element (108) according to the method (500) of one of the preceding claims.

5. Motor vehicle (200) with at least partially electric drive and with an air conditioning unit (100) according to claim 4.

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